Thinking Machines Co-founder Lilian Weng Steps Down for Health Reasons, Then Joins OpenAI

Lilian Weng, co-founder of Thinking Machines, announced this week that she would step down from her role, citing health issues. In an internal Slack message—which she also shared on X—Weng wrote, “I don’t feel I’m able to continue at the pace a startup requires. After thinking about it for several months, I ultimately have to admit that the amount of consistent stress and workload have pushed me beyond what my health can sustain physically.” On Wednesday, OpenAI confirmed to TechCrunch that Weng would rejoin the company, where she previously served as Vice President of AI Safety Research. According to a company spokesperson, she will lead a top-level team focused on accelerating OpenAI’s internal research. The team’s mission includes supporting cross-research work on recursive self-improvement—a process that enables an AI system to iteratively enhance itself, potentially leading to more powerful capabilities. At first glance, this move might seem contradictory to Weng’s statements about the health impact of fast-paced startup work. However, by moving to OpenAI as an employee rather than a co-founder, she is likely to face less direct pressure. Still, in 2026’s fiercely competitive AI talent landscape, this high-profile departure is notable. Thinking Machines co-founder Mira Murati, also a former OpenAI CTO, replied to Weng’s X post, expressing support for prioritizing health. “We’ll miss you, it’s been wonderful building Thinky together. I’m glad that you’re putting your health first. Thank you for everything,” Murati wrote. It remains unclear whether Murati was aware that Weng would rejoin OpenAI. Weng’s public message on X concluded with a reflective note: “The future worth building is human.” Her role at OpenAI marks a new chapter, as she takes on leadership in recursive self-improvement research—a critical area as AI labs race to advance autonomous systems while managing ethical and operational risks.

via TechCrunch AI